The ionic liquid can be said as ambient temperature molten salt, and is composed of cation component and anion component, for example, has properties of high heat-resistance, wide temperature range in a liquid state, non-volatility, high ionic conductivity, high solubility to polymer or salt, and the like.
The ionic liquid having such properties is expected to have application to various fields, for example, uses such as solvent for chemical reaction, electrolyte for electrochemical device, antistatic agent, lubricant, are expected.
A number of ionic liquids having a fluorine atom as anion component (for example, N(CF3SO2)2−, CF3SO3−, BF4—, PF6−, and the like) are reported, but these ionic liquids having a fluorine atom have problems such as adverse effect for ecology due to generation of halogen compound, for example, by thermal decomposition, corrosion of equipment, high production cost due to high content of fluorine.
On the other hand, as the ionic liquid having non-halogenic anion, for example, the ionic liquid using organic acid anion such as anion derived from camphor sulfonic acid (non-patent literature 1), anion derived from sulfosuccinic acid (patent literature 1), for example, the ionic liquid having anion other than organic acid anion such as cyanomethide anion (non-patent literature 2), dicyanamide anion (non-patent literature 3), tetrazole anion(non-patent literature 4) have been developed.
However, the ionic liquid having these organic acid anion has the problems that viscosity is relatively high even though melting temperature shows low, and the like, in addition, the ionic liquid having non-halogenic anion other than organic acid anion has the problems that many synthetic processes are needed, therefore, operation is complicated, expensive raw materials such as silver salt are needed for the necessary salt exchanging, furthermore, uses thereof are limited because metal(silver) ion is contaminated to the ionic liquid obtained by salt exchanging, and the like.
In addition, as ionic liquid having lower alkane sulfonate even in organic acid anion, for example, 1-butyl-3-methylimidazolium methanesulfonate, 1,3-dimethylimidazolium methanesulfonate, 1-butyl-3-methylimidazolium 2-butanesulfonate, and the like have been developed (patent literature 5, non-patent literature 2, non-patent literature 3). However, they have also problems of high melting point.
Furthermore, ionic liquid obtained by disappearing polymerizability of polymeric functional group of salt monomer consisting of cation having polymeric functional group and anion having polymeric functional group have been developed (patent literature 6).
However, this ionic liquid is the one obtained by finally disappearing polymerizability of polymeric functional group, therefore, no polymeric functional group exists in cation or anion. Also, ionic liquid containing allylsulfonate anion as anion, is not specifically disclosed.
Under such circumstances, novel ionic liquid, which has low production cost, and is environment-friendly, and has low melting point and viscosity, is desired to be developed.